Check valves may be used to selectively fluidly connect a first hose with a second hose. More specifically, check valves known in the art may be used to permit fluid flow in a first direction and to prevent or restrict flow in a second, opposite direction. One such known check valve includes a first hose connector housing, a second hose connector housing, and a membrane disk of flexible material positioned between the two hose connector housings. The membrane disk is selectively sealingly seated on a valve seat to selectively separate the first and second hoses from each other. Specifically, when unaffected by external forces the membrane disk is seated on the valve seat. However, the membrane disk becomes unseated and permits fluid connection between the first and second hoses when a sufficient external force acts on the membrane disk, such as fluid pressure from fluid flowing along the first hose. More specifically, the membrane disk defines openings located radially outwardly from the valve seat that permit fluid flow therethrough when the membrane disk is unseated, thereby connecting the first and second hoses. Such a design is disclosed European patent 0 612 537, and German Utility Model 20 2004 009 358.8, the entire contents of each of which are incorporated herein by reference.
In the medical technique, check valves may be used for the lines of infusion systems, syringes, diagnosis equipment, intravenous hose lines, in connection with syringe pumps, and the like. Check valves used for medical applications preferably have closing times of a few fractions of a second and are able to close safely to avoid any reflux of possibly contaminated fluids. Therefore, such check valves are preferably statistically accurate. Additionally, because check valves used in medical applicants are typically a single-use product, such check valves are also preferably relatively inexpensive and easy to manufacture.
Furthermore, medical and/or governmental regulations and/or other legal provisions and standards may require uniform safety functions. For example, in Germany, medical devices must be approved before they are able to be generally used in medical applications.
One such known check valve design includes a membrane disk with an annular protrusion received within annular grooves defined by the first and second hose connector housings. This design causes the membrane disk to have a relatively, radially-tight fit such that the seal between the membrane disk and the valve seat is relatively consistent, that is, the fluid pressure required to unseat the membrane disk is relatively consistent. Additionally, the radial tension forces acting on the membrane disk cause relatively fast action between the membrane disk and the valve seat.
However, it is desirable to have available check valves of varying opening pressures for different applications and/or for use with patients having varying characteristics. For example in connection with the use of syringe pumps, it is desirable to prevent the pump from running empty due to the difference in height between the patient and syringe pump since the valve could already be open because of the geodetic height. Since such valves however usually are assembled from injection molded parts, the production of valves having different opening pressures may lead to substantial costs of the molds.
During use of known check valves, relatively high fluid pressure from the entry hose may cause the membrane disk to be unseated by an undesirable distance, such that the openings in the membrane disk contact a wall of the second tube connector housing and are obstructed or partially obstructed, thereby undesirably blocking or restricting fluid flow to the second hose.
It is therefore desirable to provide a check valve that meets medical and legal standards, that is relatively simple and economical to manufacture, that may be manufactured with varying characteristics in a simple and economical manner, and that prevents or minimizes undesired closing of the check valve due to relatively high entry pressures or high differential pressures.